I have absolutely no experience with them, have never even seen one until now. Which in its own way suggests there would be no reason to use them. If valve rotators were neccesary, it seems you would see them on all engines. Just looks like one more thing to fail. Even at full load these engines aren't really all that stressed.
As usual, wait to hear from Pre '68 Dave.
Those rotators were standard equipment on heavier-duty engines from 1954 onwards (and is shown in the 1954 Master Parts Catalog as being used in non-Powerglide engines from 1941 onwards). As shown in the 1954 Engineering features manual,
the style of the rotator changed in 1954.
A warning is often given in manuals that a 45 degree valve angle is needed.
I think an exhaust valve rotator became standard equipment on all 235/261 engines in the later 50s.
In 1954, the stated value of the rotators was to prevent "excessive heat generation on heavy duty trucks or other operations where this condition may be encountered".
I think the standard use of valve rotators coincided with the change to the highest compression 235s and ~150hp. This was discussed in an earlier post about the highest compression 235 heads, and if this highest compression was due to a change in the head or to some other change.
That part number shown by George is also shown in a
1970 Master Parts Catalog for use on 1955 and earlier 6 cylinder non-Powerglide engines - a warning was again given regarding the type of valve and the valve angle (and the type of exhaust valve).
